Spectral Efficiency Analysis of Downlink Cell-Free RAN System with Zero-Forcing Beamforming

A cell-free radio access network (CF-RAN) is a novel architecture that can effectively solve the scalability problems and lack of collaboration capabilities of other cell-free networks and achieve a better trade-off between performance and complexity. There are multiple edge distributed units (EDUs) in a CF-RAN system and each EDU mounts multiple APs. This paper inves-tigates the spectral efficiency (SE) performance of a downlink CF-RAN with zero-forcing (ZF) beamforming in the presence of pilot reuse, considering power coefficients and compression noise. An asymptotic expression for the downlink signal-to-interference-plus-noise ratio (SINR) of the system can be derived by using large-scale random matrix theory. To improve the performance of the system, we consider the EDU-AP association strategy and propose a heuristic greedy algorithm. Simulation results verify the accuracy of the asymptotic expression and the effectiveness of the proposed association algorithm.